The present invention relative generally to a tachogenerator and, more specifically, to a tachogenerator having improved signal output. Means for determining the rotary speed of rotary machines of any kind, in particular electric machines, sometimes in combination with the simultaneous determination of the angular position of the rotary part, are required for a plurality of applications and machines, for example in order to control the rotary speed of certain rotary drives, or in order to derive certain information from the momentary speed, for example for use as actual values for regulating or control purposes.
In the case of certain types of electric machines, which generally can be regarded as synchronous machines and may be described, from the functional point of view, as sort of brushless d.c. motors, it is important, in addition to gaining an actual-value signal indicating the rotary speed, to derive at least relative information on the respective rotor position so that one can determine from the position of the rotor which of the coils must be excited for generating corresponding magnetic fields for the operation of such an electric motor.
Quite generally, tachogenerators have been known in numerous configurations, depending on the demands placed on their accuracy for example as incremental pick-ups, using Hall generators, optoelectric means, or the like. Usually, and in most cases necessarily, such tachogenerators have associated with them a plurality of additional processing circuit components which serve, for example, for linearizing, amplifying or preparing the signals so obtained for further processing, for example for speed regulation. This is necessary because the useful level gained is very low in most of the cases and one cannot, therefore, do without such supplementary electronic means.
Now, it is the object of the present invention to provide a tachogenerator for use in connection with rotary drives of any nature, preferably improved by the addition of supplementary means for determining the rotary speed of the driving machine, which is of simple design and supplies immediately a perfectly linearized and, accordingly, highly precise output signal of high useful level.
In a different context it has been known, in connection with an inductor for rotary electric machines (AT-PS 219 701) to build up a stationary magnet system and a rotor supplying rotary energy in axial layers in which case flat windings and laminar conductors are arranged on the rotor. Due to the arrangement in axial layers, a plane air gap is obtained between the rotor and the stator parts. The stator part comprises a plurality of permanent magnets each of which is connected in parallel, via a common yoke, to a magnetic subsidiary circuit comprising an electric excitation winding. The parallel subsidiary circuits, therefore, contribute very specially towards generating the inductor flux in the machine when the excitation winding is excited, while a magnetic short-circuit is produced for the respective permanent magnet of the stator part when the excitation winding is interrupted. There does not exist any relation to the present invention.